Applications such as Time Difference of Arrival (TDOA) or Time of Arrival (TOA) methods for location determination rely on tight synchronization of the clocks of a plurality of devices such as access points. For example, with TDOA, for every nanosecond of uncertainty between access point (AP) clocks there is a foot of uncertainty in the spatial solution. AP clocks, for example, are naturally unsynchronized because of slight differences in the quartz crystals used to set clock frequencies. In addition, clock variations may occur due to temperature, age, and clock jitter. Further, applications such as beam-forming and multi-user multiple-input multiple-output MIMO (MU-MIMO) apply pre-coding to baseband signals which may rely on precise phase and frequency coherence across all signal paths. In addition these applications may require the tight synchronization of transmission of the same wireless signal from multiple APs in a network.
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation.